Proposal Information for 2010A-0167

Abstract:
Theories of binary star evolution predict that an early F dwarf star
will sometimes be paired with a hot subdwarf (an ``sdB'' star). This is
an essential prediction from theories that successfully account for
pairings of sdB stars with white dwarf or lower-mass stars, but only a
few F+sdB systems have been studied previously. Their space density in
the disk of the Galaxy needs to be determined. The distribution of
orbital periods of the F+sdB systems, which depends on the processes of
mass transfer/loss and angular momentum loss from the binary, needs to
be established. Observations of F+sdB pairs provide a new way to help
test and improve binary population synthesis (BPS) models, which are
used throughout astrophysics to understand a wide variety of exotic
objects and to predict their numbers. Using 2MASS and GALEX archival
data, it is possible to identify early F star candidates with UV
excesses (F+UVX). The 2.1m telescope with GoldCam spectrograph will be
used to classify these color-selected F+UVX candidates on the MK system,
reject interloping Algol systems and other objects that mimic F-star
colors, and develop a representative sample of F+UVX stars that will be
observed synoptically at high spectral resolution to obtain
spectroscopic orbits. For a sample of stars that can be observed
synoptically throughout the year and be of use to other observers, the
entire range of RA needs to be included; this proposal for 2010A
complements a similar proposal which has been awarded time in 2009B, to
provide the necessary MK classifications and other validation in the
remaining RA range.